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1
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Dielectric Properties of Isatomalononitrile

100%
Khalil S., Hassaan A.
Acta Physica Polonica A
|
1993
|
vol. 83
|
issue 4
477-480
EN
The paper reports dielectric measurements carried out for isatomalononitrile at different temperatures (346 to 383 K) and various frequencies (50 to 5 × 10^{5} Hz). Kramers-Kronig relations are used to ascertain the magnitude of the dc conductivity and to enhance the reliability of dielectric measurements. The analysis of the results shows that there exist certain very slow dielectric phenomena in isatomalononitrile. The frequency dependent conductivity of isatomalononitrile increases approximately linear with frequency. The frequency exponent has the value of 0.5, independent of temperature.
2
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Dielectric Properties of Triglycine Sulphate Crystals Admixtured With D- and DL-Phenylalanine

100%
Stankowska J., Peter E., Trybula M.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 6
1061-1072
EN
The paper reports studies on the effect of D-phenylalanine and DL-phenylalanine admixtures on dielectric properties and domain structure of triglycine sulphate crystals. Permittivity ε and loss tangent tgδ were measured in a wide range of temperatures (10-340 K) as a function of measuring field varied from 1 to 10000 kHz, for samples cut out from two growth pyramids (001) and (110) from triglycine sulphate crystals containing different concentrations of admixtures. A comparison of the effects of D-phenylalanine and DL-phenylalanine admixtures on dielectric properties of triglycine sulphate crystals was made. With increasing concentrations of admixtures in the crystals, the values of ε_{max} decreased while E_{c} and E_{b} (bias field) increased, and P_{s} and T_{c} showed insignificant changes. Observations of the domain structure of the admixtured crystals by the liquid crystal method proved its refinement and irregularity. Changes in the domain structure of the crystals occurring in the process of spontaneous ageing were analysed.
3
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AC Conductivity and Dielectric Properties οf Amorphous Te_{42}As_{36}Ge_{10}Si_{12} Glass

63%
Hegab N., El-Mallah H.
Acta Physica Polonica A
|
2009
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vol. 116
|
issue 6
1048-1052
EN
Te_{42}As_{36}Ge_{10}Si_{12} chalcogenide composition was prepared by conventional melt-quenching. The ac conductivity and the dielectric properties were carried out in the frequency range 0.5×10^{3}-4×10^{6} Hz and temperature range 300-423 K. The analysis of the experimental results of the frequency dependence of ac conductivity σ_{ac}(ω) indicates that σ_{ac}(ω) is proportional to ω^{s} where s> 1. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping model. The maximum barrier height W_{m} calculated from ac conductivity and the density of localized states were determined. Values of dielectric constant ε_{1} and dielectric loss ε_{2} were found to decrease with frequency and increase with temperature. The analysis of dielectric loss leads to determine the barrier height W_{m} and agrees with that proposed by the theory of hopping of charge carriers over potential barrier between charged defect states as suggested by Elliott in case of chalcogenide glasses.
4
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Ac Conductivity Measurement of Cd_{5}Se_{95-x}Zn_{x} Chalcogenide Semiconductor Using Correlated Barrier Hopping Model

63%
Ganaie M., Zulfequar M.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 1
59-63
EN
Cd_{5}Se_{95-x}Zn_{x} (x=0, 2, 4, 6) chalcogenide semiconductors were prepared by conventional melt-quenching and were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared studies. Ac conductivity of Cd_{5}Se_{95-x}Zn_{x} chalcogenide semiconductor has been investigated in the frequency range of 1 kHz-1 MHz and in the temperature range of 290-370 K. The analysis of the experimental results indicates that the ac conductivity is temperature, frequency and concentration dependent. Ac conductivity is found to obey the power law ω^{s} where s < 1. A strong dependence of ac conductivity and exponent s can be well interpreted in terms of correlated barrier hopping model. The maximum barrier height W_{m} were calculated from the results of dielectric loss according to the Guintini equation that agree with the theory of hopping of charge carriers over potential barrier as suggested by Elliot in case of chalcogenide semiconductors.
5
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Ac Conductivity and Dielectric Properties of Amorphous Ge_{15}Se_{60}X_{25} ( X = As or Sn) Films

63%
Hegab N., Afifi M., Atyia H., Ismael M.
Acta Physica Polonica A
|
2011
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vol. 119
|
issue 3
416-423
EN
The ac conductivity and dielectric properties of Ge_{15}Se_{60} X_{25} (X = As or Sn) thin films are reported in this paper. The thin films were deposited by thermal evaporation at 10^{-5} Torr pressure. The films were well characterized by X-ray diffraction, differential thermal analysis and energy dispersive X-ray spectroscopy. The ac conductivity was measured over temperature range 303-413 K and frequency range 10^2-10^5 Hz. The frequency dependence of the ac conductivity was found to be linear with slope which lies very close to unity and is independent of temperature. This behavior can be explained in terms of the correlated barrier hopping between centers forming intimate valence alternation pairs. Values of the dielectric constant ε_1 were found to decrease with frequency and increase with temperature. The maximum barrier height W_{m} for each sample, which was calculated from the dielectric measurements according to the Guinitin equation, agrees with the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized state near the Fermi level was estimated for the studied films.
6
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Effect of Annealing Temperature on the Electric and Dielectric Properties of Se_{70}Te_{15}Bi_{15} Films

63%
Atyia H.
Acta Physica Polonica A
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2014
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vol. 125
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issue 1
98-104
EN
The effect of annealing at different temperatures between T_{g} and T_{c} on the AC conductivity and dielectric properties was studied for Se_{70}Te_{15}Bi_{15} films grown by thermal evaporation technique. The films were characterized by X-ray diffraction, differential thermal analysis, and energy dispersive X-ray spectroscopy. X-ray diffraction analysis shows the occurrence of amorphous to polycrystalline transformation for films annealed at annealing temperature T_{a} ≥ 473 K. AC conductivity σ_{AC}(ω) was studied as a function of T_{a}, frequencies (0.1-100 kHz) and working temperatures (303-393 K). It was found that σ_{AC}(ω) obeyed Aω^{s} law. According to the values of s and its temperature dependence, the AC conduction mechanism was determined in terms of the correlated barrier hopping and quantum mechanical tunneling models for the as deposited and annealed films, respectively. The DC and AC activation energies were determined as a function of T_{a}. Values of dielectric constant ε_1 and dielectric loss ε_2 were found to increase with increasing T_{a}. A Debye-like relaxation of dielectric behavior was observed for polycrystalline films, and was found to be a thermally activated process.
7
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Dielectric Properties of Magnetic Liquids in High Electric Fields

63%
Herchl F., Kopčanský P., Timko M., Koneracká M., Marton K., Kolcunová I., Tomčo L.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
569-572
EN
In this work, dielectric properties of magnetic fluids composed of magnetite particles dispersed in transformer oil and subjected to a uniform magnetic field were investigated at the high alternating electric field intensities in the range of 0.5-2.5 MV/m. Dielectric stability of the magnetic fluid with the particle volume concentrationΦ= 0.0019 was observed. The magnetic fluid with the concentrationΦ= 0.019 showed the significant changes of permittivity and dielectric losses, too.
8
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Content available

Positron Annihilation Lifetime Spectroscopy and Dielectric Measurements of Natural Kaolinite and Kaolinite Intercalated by Potassium Acetate

51%
Leluk K., Orzechowski K., Jerie K., Baranowski A., Słonka T., Głowiński J.
Acta Physica Polonica A
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2006
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vol. 110
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issue 5
621-629
EN
Intercalation of clay minerals consists in inserting of guest molecules into interlayer area. It results in expanding the interlayer distance and changes of physical and chemical properties of the material. Dielectric spectroscopy, positron annihilation lifetime experiments, X-ray, and thermoanalysis were jointly applied to investigate the structural changes accompanying intercalation.
9
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Application of High Permittivity Bismuth Copper Titanate in Multilayer Capacitors

51%
Szwagierczak D., Kulawik J.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 1
119-121
EN
A nonferroelectric high permittivity compound with the perovskite structure, Bi_{2/3}Cu_3Ti_4O_{12}, was synthesized at 900°C. The ceramic powder and appropriate organic additives were used for preparation of a slurry for tape casting. The obtained green tapes were smooth, flexible, and with a uniform thickness of 25 μm after drying at 50°C. Ag electrodes were screen printed on green rectangular sheets cut by a laser. Subsequent operations were screen printing of Ag internal electrodes, stacking of green sheets, isostatic lamination, cutting, deposition of external terminations and co-firing of dielectric and conductive layers at 850°C. Scanning electron microscopy observations showed well sintered, dense, fine-grained microstructure of ceramic layers and good cooperation with the electrodes made of commercial Ag paste. Capacitance and dissipation factor of multilayer capacitors were examined in the temperature range from - 55 to 330C at frequencies 10 Hz-2 MHz. The fabricated multilayer capacitors exhibit high capacitance and relatively low temperature coefficient of capacitance in the temperature range from - 55 to 110°C. The obtained lead-free high permittivity nonferroelectric material Bi_{2/3}Cu_3Ti_4O_{12} is a spontaneously formed internal barrier capacitor. This material seems to be a promising alternative for conventional lead-based relaxor dielectrics in multilayer ceramic capacitors.
10
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Kinetic Theory of the Langevin Saturation in Dilute Solution of Dipolar Symmetric-Top Molecules in Spherical Solvents

51%
Alexiewicz W., Grygiel K.
Acta Physica Polonica A
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2008
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vol. 114
|
issue 4
667-686
EN
Assuming the low molecular reorientation approximation, the formulae for the third-order electric polarization induced in liquids composed of rigid noninteracting dipolar, symmetric-top molecules in spherical solvents were derived. Our medium is acted on by a strong external dc bias electric field superimposed on a weak ac electric field, and the classical Smoluchowski-Debye equation for rotational diffusion of the symmetric-top molecules is applied. In order to highlight the influence of the anisotropy of rotational diffusion tensor components and the orientation of permanent dipole moment of the molecule on the complex linear and nonlinear electric susceptibilities, we present three-dimensional plots of the linear and nonlinear dispersion and absorption spectra, for different values of the frequency of ac electric field.
11
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Cole-Cole Plots for Linear and Nonlinear Dielectric Relaxation in Solutions of Rigid Highly Dipolar Symmetric-Top Molecules in Spherical Solvents

51%
Alexiewicz W., Grygiel K.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 4
687-698
EN
The graphical analysis of the influence of the rotational diffusion tensor anisotropy and the orientation of the permanent dipole moment on the linear and nonlinear dielectric relaxation is shown. The solution of Smoluchowski-Debye rotational diffusion equation for rigid, and noninteracting polar, symmetric-top molecules, in the "weak molecular reorientation approximation", was used. In order to highlight the influence of the symmetric shape of molecule, in comparison with classical, spherical-top Smoluchowski rotational diffusion, we present sets of Argand-type plots and three-dimensional Cole-Cole diagrams for linear and nonlinear electric susceptibilities. The results indicate that, in describing the nonlinear dielectric relaxation, the simplest spherical-top rotational diffusion model may be a sufficient approximation in some special cases only.
12
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Birefringent and Dielectric Properties of [N(C_{2}H_{5})_{4}]_{2}ZnBr_{4} and [N(C_{2}H_{5})_{4}]_{2}CdBr_{4} Crystals

51%
Sveleba S., Mokryi V., Polovinko I., Kapustyanik V., Trybuła Z., Petrenko P., Kiosse G., Kravtsov V.
Acta Physica Polonica A
|
1993
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vol. 83
|
issue 6
777-784
EN
Dielectric and birefringent properties of [N(C_{2}H_{5})_{4}]_{2}ZnBr_{4} and [N(C_{2}H_{5})_{4}]_{2}CdBr_{4} crystals were investigated. It has been ascertained that two phase transitions manifest themselves in the temperature dependencies є(T) for [N(C_{2}H_{5})_{4}]_{2}CdBr_{4} crystal - a second-order transition at T_{1} = 311 K and a first-order one - at T_{2} = 39 K (∆T_{2} = 11 K). Besides two earlier known phase transitions in [N(C_{2}H_{5})_{4}]_{2}ZnBr_{4} at T_{1} = 350 K and T^{cool}_{2} = 282.8 K (∆T_{2} ≈ 2.3 K), the additional one was found at T*_{2} = 287.0 K, both on the cooling and heating runs. On the basis of the data about the peculiarities of dielectric and optical properties in the vicinity of T_{2} one can made the conclusion about the ferroelectric character of the phase, situated between T*_{2} and T^{cool}_{2}.
13
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Studies on Structural, Dielectric, and Electrical Properties of a Ni_{0.284}Zn_{0.549}Cu_{0.183}Fe_{1.984}O₄ Piezomagnetic Material

51%
Balusamy R., Kumaravel P., Kanagathara N., Gowri Shankar Rao R., Renganathan N.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 3
751-757
EN
Piezomagnetic materials in composition Ni_{0.284}Zn_{0.549}Cu_{0.183}Fe_{1.984}O₄ were prepared by mixed oxide method at 1100°C. Powder X-ray diffraction studies confirm the crystalline nature of the synthesized Ni_{0.284}Zn_{0.549}Cu_{0.183}Fe_{1.984}O₄ piezomagnetic material. The crystallite size is calculated to be 19.332 μ m using the Debye-Scherrer formula. The surface morphology and particle size of the samples has been studied by scanning electron microscopy. The thermal stability and decomposition behaviour of Ni_{0.284}Zn_{0.549}Cu_{0.183}Fe_{1.984}O₄ piezomagnetic material have been studied by thermogravimetric analysis at a heating rate of 15°C/min. The effective activation energy of the prepared composite was calculated using single heating rate methods: Broido's and Coats-Redfern methods. Dielectric properties of Ni_{0.284}Zn_{0.549}Cu_{0.183}Fe_{1.984}O₄ piezomagnetic material have been studied in a wide range of frequencies and temperatures. The magnetic behavior of Ni_{0.284} Zn_{0.549} Cu_{0.183} Fe_{1.984}O₄ piezomagnetic material at room temperature has been confirmed by vibrational sample magnetometer studies.
14
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Dielectric Relaxation Phenomena in SBN Single Crystals Doped with Ce

51%
Korchak Y., Kapustianyk V., Fedor B., Girnyk I., Eliyashevskyi Y.
Acta Physica Polonica A
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2011
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vol. 119
|
issue 6
871-874
EN
The dielectric study of Sr_{0.73}Ba_{0.27}Nb_2O_6:Ce (SBN) crystals along [010] crystallographic axis was performed in the temperature region of 310-360 K and frequency range from 25 Hz up to 1 MHz. The thermal dipole relaxation of quasi-Debye-type for this orientation of sample was observed in both investigated structural phases. The phase transition was most clearly seen from the temperature dependence of the relaxation time at T_{c} = 320 K. The relaxation processes were related to the collective oscillations of the Nb-O bonds in the two different type corner-sharing NbO_6 octahedra aligned along c-axis.
15
Content available remote

IR Resonant Absorption in Molecular Nanofilms

51%
Pelemiš S., Šetrajčić J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
579-584
EN
The paper presents a theoretical research of changes of optical properties of various nanofilm molecular crystals which are caused by the presence of two parallel and close borders. We used combined analytical-numerical calculation to find the allowed energy states of excitons and their spatial distribution (per layers) along the axis perpendicular to surface planes. We determined permittivity for the observed models of these ultrathin dielectric films and explored the influence of boundary parameters on the occurrence of discrete (per frequencies) and selective (per layers) absorption. The conditions for occurrence of smallest number of resonant absorption lines have been found and their localization has been defined.
16
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Structural, Electrical and Mössbauer Effect Studies of 0.5Bi rm_{0.95}Dy_{0.05}FeO_3-0.5Pb(Fe_{0.5}Nb_{0.5})O_3 Multiferroics

51%
Stoch A., Kulawik J., Stoch P., Maurin J., Zachariasz P.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1585-1590
EN
0.5Bi_{0.95}Dy_{0.05}FeO_3-0.5Pb(Fe_{0.5}Nb_{0.5})O_3 is a multiferroic material which exhibits ferroelectric and antiferromagnetic ordering. (The synthesis of such compounds is rather difficult.) In this paper the way of the synthesis of 0.5Bi_{0.95}Dy_{0.05}FeO_3-0.5Pb(Fe_{0.5}Nb_{0.5})O_3 is presented. The detailed X-ray and Mössbauer effect studies were done and crystal and hyperfine interaction parameters were obtained. To measure electrical properties of the compound the impedance spectroscopy measurements were performed. The obtained impedance spectra were fitted using a proposed equivalent electrical circuit and the results were discussed in the scope of the brick layer model without easy paths.
17
Content available remote

On the Frequency Domain Relaxation Processes in Gallium Doped CdTe and Cd_{0.99}Mn_{0.01}Te

51%
Trzmiel J., Płaczek-Popko E., Zielony E., Gumienny Z.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
956-958
EN
The dielectric response of gallium doped Cd_{0.99}Mn_{0.01}Te and CdTe alloys possessing DX centers was studied by impedance spectroscopy. Complex modulus and impedance spectroscopic plots were analyzed. Near ideal Debye response of CdTe:Ga was observed, whereas for Cd_{0.99}Mn_{0.01}Te:Ga samples non-Debye behavior was stated. Different relaxation responses may be related to various local atomic configurations in the vicinity of the DX centers in the studied materials.
18
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Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters

51%
Mikułko A., Fraś M., Marzec M., Wróbel S., Ossowska-Chruściel M., Chruściel J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1155-1160
EN
The main objective of this paper is to study dielectric properties of two compounds of acronyms 5OSCl and 6OSCl having strongly polar bond (C-Cl) at para position. Dielectric measurements were done in the frequency range from 40 Hz to 15 MHz. The dielectric spectra were measured for two principal alignments. For homeotropic alignment, the reorientation of molecule around the short molecular axis was observed. Both substances studied exhibit large positive dielectric anisotropy and the anisotropy of conductivity was obtained in smectic A as well as nematic phase.
19
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Magnetoelectric Properties of 0.3Bi_{0.95}Dy_{0.05}FeO_3-0.7Pb(Fe_{2/3}W_{1/3})O_3 Multiferroic

45%
Stoch A., Stoch P., Kulawik J., Zieliński P., Maurin J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
128-130
EN
Pb-based complex perovskites with Fe^{3+} like Pb(Fe_{2/3}W_{1/3})O_3 were found to be interesting because of their unique properties such as relaxor and magnetoelectric behavior. Pb(Fe_{2/3}W_{1/3})O_3 is ferroelectric with ferroelectric Curie temperature T_{C} between 150 and 200 K and at the same time is antiferromagnetic with magnetic Néel temperature about 400 K. BiFeO_3 is a well known perovskite compound which exhibits ferroelectric (T_{C} = 1103 K) and antiferromagnetic (T_{N} = 643 K) ordering simultaneously. The polycrystalline sample of 0.3Bi_{0.95}Dy_{0.05}FeO_3-0.7Pb(Fe_{2/3}W_{1/3})O_3 were synthesized using standard sintering procedure. Magnetization vs. magnetic field (at 4.2 K) curves were measured. Magnetoelectric properties of the sample were obtained.
20
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Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

45%
Szwagierczak D.
Acta Physica Polonica A
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2012
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vol. 121
|
issue 1
205-207
EN
A new perovskite material Nd_{2/3}CuTa_4O_{12} was applied as a naturally formed internal barrier layer capacitor. The powder prepared by solid state synthesis and ball milling was pressed into pellets and sintered at 1180-1220°C. Dielectric properties of ceramic samples were characterized by impedance spectroscopic studies carried out in the temperature range from - 55 to 700C at frequencies 10 Hz ÷ 2 MHz. Two types of the dielectric response were revealed - a high frequency response attributed to grains which occurred at low temperatures, and a low frequency one related to grain boundaries which dominated at higher temperatures. Resistances and capacitances of grains were found to be two orders lower than those of grain boundaries. Two plateaus were observed in the dielectric permittivity versus frequency plots - a low frequency step corresponding to a high value of 10^4 and a high frequency step at a level of 40. Scanning electron microscopy observations and energy dispersive spectroscopy analysis confirmed that Nd_{2/3}CuTa_4O_{12} ceramics were composed of semiconducting grains and insulating oxygen-enriched grain boundaries. The formation of such an electrically heterogeneous system during the one step fabrication process in air leads to spontaneous internal barrier layer capacitance effects responsible for a high and relatively stable dielectric permittivity of the developed material.
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